Configuration of optically active phosphorus thioacids—II

Abstract

Rotations at the NaD line, CD and UV spectra of a series of O-alkyl alkylphosphonothioic acids, two alkylphenylphosphinothioic acids and their respective derivatives were measured. In the case of the phosphonothioic acid derivatives containing the PS bond the correct sign of rotation at the NaD line could be predicted by the application of Brewster's conformational asymmetry rule. A simple rule is given for correlating the sign of the Cotton effect around 200–230 nm with the configuration. In the CD spectra of the aromatic phosphinothioic acid derivatives at least four bands have been found whose assignments are discussed. The CD of the nondissociated acid (in nonpolar solvents) is analogous to that of homochiral ester derivatives; it is different in water solution, where the dissociated acid forms a new chromophore. According to the CD, the P(S)OH tautomeric form is preferred for the phosphono- and phosphinothioic acids.